Feed dog and throat plate for compound feed sewing machines



C. L. THORNE June 18, 1963 FEED DOG AND THROAT PLATE FOR COMPOUND FEED SEWING MACHINES Filed Nov. 23, 1960 IN VEN TOR. CHARLES L. THORNE WITNESS ATTORNEY.

United States Patent 3,094,087 FEED DOG AND-THROAT PLATEFORYCOM- POUND "FEED ,SEWING MACHINES -C harles.L. Thorne, Garwood, NJ.,- assignor to The Singer rManufacturing Company, Elizabeth, NJ a corporation .ofiNewQJersey invention relatesto-sewing machines having compound 'wor-k feeding mechanisms, that is,..a mechanism in whichfitheneedle moves in the lineof -feed in synchronism wanna teed 'dogand the*feeding occurs while the needle is in the goods. More particularly; this invention relates to anovel: and improved feeddogand throat plate combination for compound feed sewing machines.

It is an object of this iinvention-to provide a feed dog and throat *plate combination fora compound feed -sewing machine which is highlyeffective inchaining oft, i;e., in influencing properthread concatenation when there is no longer any work fabrics beneath the sewing machinei presser foot.

Ano'ther 'objectof this invention is to provideia feed dog and-throat platecombinationfor a compoundfeed --sewing machine-in-which the workfabrics beingstitched are manipulated in a novel and effective manner to pre- -vent flaggingof thework duringthe setting of stitches :therein.

"It-is also an 'object of this invention to provide -a 'ieed *dog'and throatplate combination in which the feed dog is provided 'Witha platform-beneath thethroat'plate and --with a novelaa-nd effective meansfor preventing the. accumulation of linton the feed dog platform.

With-the aboveand other objects and advantages in -view as willhereinafter appear, this invention comprises the devices, combinations, and arrangements of parts hereina'fter describe'd and illustrated in the accompanying drawings of -a preferred embodiment in which:

FIG. 1 represents a top-plan viewof a 'sewingmachine cloth plate having a throat .plate and a feed dog alapplied thereto; in; accordance JWithiihiSuiIlVt-HlfiOIl,

:FIG. "2 is: anenlarged'cross i sectional view takeniisub- 'lstantially along line ".2'2 of FIG. 1 -\and'including a :portion of the :sewingtmachine needle :and fthesewing 1 threads,

I'FIG. 3 His i-aecross :sectional view taken substantially salong'line;3-+3 of FIG. land including ithersewing machine presser foot, needle, and the sewingzthreadiwith t the needle aan'dfeed :dogillustrated-"at theibeginning of .needle zpenetrationgandwat' the start of: the work :feeding motion,

QEIG. =4miS a cross sectional View-taken substantially .;a1ong;,line 13-.3 :of :F BIG. :1? similar ;to :FIG. *3 abut: with s the: parts illustrated upon Withdrawal of the t needle: and ata the conclusion: of 1 the ,-W01'k feeding motion, and

1'FIG.. 5 representssa; perspective view of the feed-:dog -,.'of=;this;invention.

rReferri-ngto the drawing, :a fragmentof thevwork. supportingwclothplate-j of" arsewi-ngmachine is illustratedat 11 and, as -!ShOWI1*lIlrFIG- ,1, the cloth plateais fitted :withra throat plate-.12 secured: by screws 13. The throat =-plate :12: is formed w-ith 1 spaced rectangular. feed dog accommodating,- slots 14 and 115 one r-at'each side of and iparallel !t O-"a"IO.Wv Of aligned" elongate feed dogmccom- -mod;ating slots ,16. formed in the throat :plate rbetween ther'feed dog accommodating slots 14;and15 is an elongate needle aperture 17.

.Qarriednbeneathvthea cloth plate 11 and'thethroat plate ,1 2 risaatteed i-bar 20 to which is secured by screws 21 afeedldogzz. The feed ;dog is formed with: continuous ',para'llel .-raised ribs .23 and t: 24 provided with ,work engaging ,serra'tions and adapted to operate upwardly opposite side of the eye. include a representation of the sewing threads during a :chaining-oif operationin which nowork ispresent between'thepresser foot and the throat plate. from a conventional bobbin is indicated as T while the needle thread is indicated as T fabric passes from beneath the presser foot. toperationisknownin'the art as chaining-off, and itiis 3,694,087 Patented June 18, 1963 ice through the feed dog accommodating slots 14 and 15 in thethroat plate, as illustrated in FIGS. 1 and 2. Be- .tween the :feed dog ribs 23 and 24 extends a web 25 formed with a row of aligned raised lands 26 each provided with work engaging serrations and adapted to opcrate upwardly through the feed dog accommodating slots 16 in the throat plate. The web 25 of the feed dog is formed'with two rectangular apertures 27 and 28 disposed between the lands 26 and extending substantially .the entire width of the web 25 between the continuous raised work engaging ribs 23 and 24 for the purpose of clearing lint from between the web 25 and the throat plate as'will be explainedhereinbelow. The web 25 is alsoformed with a generally triangular aperture 29 of which one side edge extends'substantially the entire width o'fiilhe web 25 between the continuou-s raisedwork engagingribs 23 and 24 and is perpendicular to the direction'offeed. From the apex of the other two side edges 'FIGS. 2, 3 and 4 illustrate a presse-r foot 31 which i-s biased downwardly against the throat plate and in op- ;position to the feed dog. These figures also illustrate a vneedle'32 formed-with a short groove 33 at one sideof the'needle ,eye 34 and with a long groove 35 at the In addition FIGS. 2, 3 and 4 The thread The sewing machine towhich this invention hasapplication is of the variety known in the .art as a compound feed machine in which there is imparted to the needle, inuadditio-n to endwise reciprocation, movements in the direction of feed. Themechanismdor imparting such. endwise and work feeding motionsto the :needle rnay be of anyfknown form. The feed dog 22.partakes ofconventional tour motion movements, that is, -up .wardly intoengagement with the work, then aforward work feeding motion,downwardly out of engagement withthework, followed by areturn motion. Any known :four motion feed actuating mechanismsmay be used proin that. a.plurality of plies of work fabrics maybe advanced far more evenly and without gathering of one ofthepliesthan with work feeds located solely onone side of thework, compound feed sewing machines'have been troublesomefor severalreasons, and this. invention is directed tome-ans for obviating these disadvantages of known compound feed machines.

The compound "feedsewing machinesknown in the art have exhibited poor chaining-off characteristics. It

is extremely troublesomewhen a sewing machine fails to concatenate the sewing threads properly as a work Such an a serious and time consuming problem if a sewing machine snarls and breaks thesewing-threads as theop- -erator proceeds from one garment to the next.

To explainthe chaining-0E diificulties heretofore ex- ,periencedwith compound feed machines it must first be understood that. sewing machine needles are formed from the eye witha short groove 33 on. that-side from which the needle thread extends to thevwork-and .with a long groove 35 on that side of the eye from which the needle thread extends to the supply spool. In order properly to present a loop of needle thread between the needle eye and the work for seizure and manipulation by the stitch forming instrumentalities, such as a conventional loop taker, it is necessary that some resistance be offered to the work limb of the thread extending from the eye of the needle to the work as the needle begins to rise so that this limb of the thread will not move vertically with the needle but will be stripped off the needle and bowed outwardly to form a loop. When there are work fabrics beneath the presser foot for penetration by the needle, the work fabrics in hugging the needle provide such resistance or thread stripping action. Because of the absence of a long groove on that side of the needle from which the thread extends to the work, the resistance offered this limb of thread is greater than that on the long groove side where the thread is buried in the groove and thus loop formation on the short groove side of the needle is encouraged. When the needle does not penetrate work fabrics, the resistance on the thread to encourage loop formation must be derived elsewhere. In sewing machines in which the needle partakes of only endwise reciprocation the throat plate needle aperture can be sufiiciently small to provide the necessary resistance for loop formation, however, in a compound feed machine the needle during loop formation is being moved along the necessarily elongated needle aperture 17 in the throat plate and the thread will be wiped to one side of the needle rather than remaining constricted between the needle and one side of the needle aperture.

In the present invention, the narrow needle accommodating slot 30 of the triangular opening 29 of the feed dog provides for the resistance of the work limb of the thread on the needle to encourage proper loop formation when there is no work beneath the presser foot. Since the needle and feed dog move in synchronism in feeding the work there is no relative lateral motion between the needle and the feed dog slot 30 and, therefore, the same desirable cooperation between these parts for loop formation in chaining-off occurs as in machines in which the needle is not used in the feed of the work.

It is important to note that in the arrangement of this invention, the narrow needle accommodating slot 30 of the aperture 29 is formed in the feed dog web portion 25 which underlies the throat plate 12. This construction differs from that of a known feed dog construction for compound feed machines in which a needle aperture in the feed dog is formed in a portion of the feed dog which is raised substantially to the level of the tops of the serrated work engaging teeth thereof. In this known construction, the throat plate is cut away to provide clearance for the raised apertured feed dog portion rather than being sandwiched between the work and the apertured feed dog portion as in the construction of the invention. The prior construction has a deleterious effect upon the quality of stitch formation because, in a compound feed sewing machine, the stitches are set after the needle has been raised out of the work and during the lowered return stroke of the feed dog. Thus with the prior construction, the work in the immediate vicinity of the stitching point is freed during stitch setting and a condition referred to as flagging is common; that is, the tension applied to the sewing threads in setting the stitch causes the work which is held only about the marginal edges of the presser foot to move upwardly or downwardly, thus adversely influencing the tension at which successive stitches are set into the work.

With the construction of this machine in which the throat plate is sandwiched between the apertured web 25 of the feed dog and the work, the presser foot during stitch setting, and while the feed dog is lowered, clamps the work about the needle aperture 17 in the throat plate and closely adjacent to the stitching point such that flagging is definitely minimized.

It will be appreciated that the accumulation of lint on the web 25 is to be avoided so as not to interfere with the motion of the feed dog beneath the throat plate. The apertures 27, 28 and 29 in the web 25 provide a simple and effective means for discouraging the collection of lint, thread, and the like on the web, and for clearing any such foreign material from between the feed dog and throat plate. The edges of the apertures 27, 28 and 29 are preferably angular, as illustrated in FIGS. 2, 3 and 4, and serve during the regular motions of the feed dog to scrape any lint or the like which may find its way on the web 25 into one of the apertures through which the foreign matter will fall harmlessly beneath the machine.

The feed dog and throat plate combination of this invention thus provide the advantages in a compound feed sewing machine of highly effective chaining-off operation during periods while no work is disposed beneath the presser foot, the elimination of work flagging during stitch setting and the consequent high uniformity of stitch setting and satisfactory seam appearance, and the effective removal of lint or other foreign material from between the throat plate and the feed dog.

Having thus set forth the nature of this invention, what I claim herein is:

1. In a compound feed sewing machine, a throat plate having a portion formed with a needle aperture elongate in the direction of feed substantially the length of the longest stitch adapted to be produced by said sewing machine and with parallel feed dog slots elongate in the direction of feed and disposed one at each side of said needle aperture, a feed dog, upstanding work engaging ribs formed on said feed dog and operable upwardly through said feed dog slots in the throat plate, a web portion of said feed dog extending between said work engaging ribs and disposed beneath that portion of said throat plate formed with said needle aperture, said feed dog web being formed with a lint clearing aperture extending substantially the entire width of said web between said work engaging ribs, and said feed dog web being provided with a needle accommodating aperture formed as a narrow slot extending from said lint clearing aperture and disposed beneath said needle aperture in said throat plate.

2. A device as set forth in claim 1 in which said lint clearing aperture is of substantially triangular shape having one side edge disposed transversely across said web substantially perpendicular to the direction of feed, and in which said needle accommodating aperture in said web extends from said triangularly shaped lint clearing aperture at the apex formed by the juncture of the other two sides thereof.

3. A feed dog and throat plate combination adapted for a compound feed sewing machine, comprising a throat plate formed with a needle aperture elongate in the direction of feed, with parallel continuous feed dog slots elongate in the direction of feed and disposed one at each side of said needle aperture, and with a row of aligned elongate feed dog slots parallel to and between said continuous feed slots being and arranged at least one beyond each end of said elongate needle aperture, a feed dog, continuous upstanding work engaging ribs formed one at each side of said feed dog and operable upwardly through said continuous feed dog slots in the throat plate, a web portion of said feed dog extending between said continuous upstanding work engaging ribs and disposed beneath said throat plate, a plurality of raised upstanding work engaging lands formed on said web and operable upwardly each through one of said row of aligned feed dog slots in said throat plate, said feed dog web being formed with a plurality of lint clearing apertures extending substantially the entire width of said web between said continuous upstanding work engaging ribs and between said plurality of raised upstanding work engaging lands, and said feed dog web being provided with a needle accommodating aperture formed as a narrow slot elongate 5 in the direction of feed extending from one of said lint clearing apertures and disposed beneath said needle aperture in said throat plate.

4. A device as set forth in claim 1 in which said feed dog web is provided with a plurality of lint clearing apertures each extending substantially the entire width of said web between said work engaging ribs, and with said needle accommodating aperture formed as a narrow slot extending from one of said plurality of lint clearing apertures.

References Cited in the file of this patent UNITED STATES PATENTS Willcox et a1. June 27, 1871 Munsing May 25, 1897 Woodward et a1. Jan. 18, 1898 McNeil Apr. 16, 1918 Thompson Jan. 15, 1935 Johnson Apr. 7, 1953 Hayes Oct. 29, 1957 Reimer May 5, 1959 

1. IN A COMPOUND FEED SEWING MACHINE, A THROAT PLATE HAVING A PORTION FORMED WITH A NEEDLE APERTURE ELONGATE IN THE DIRECTION OF FEED SUBSTANTIALLY THE LENGTH OF THE LONGEST STITCH ADAPTED TO BE PRODUCED BY SAID SEWING MACHINE AND WITH PARALLEL FEED DOG SLOTS ELONGATE IN THE DIRECTION OF FEED AND DISPOSED ONE AT EACH SIDE OF SAID NEEDLE APERTURE, A FEED DOG, UPSTANDING WORK ENGAGING RIBS FORMED ON SAID FEED DOG AND OPERABLE UPWARDLY THROUGH SAID FEED DOG SLOTS IN THE THROAT PLATE, A WEB PORTION OF SAID FEED DOG EXTENDING BETWEEN SAID WORK ENGAGING RIBS AND DISPOSED BENEATH THAT PORTION OF SAID THROAT PLATE FORMED WITH SAID NEEDLE APERTURE, SAID FEED DOG WEB BEING FORMED WITH A LINT CLEARING APERTURE EXTENDING SUBSTANTIALLY THE ENTIRE WIDTH OF SAID WEB BETWEEN SAID WORK ENGAGING RIBS, AND SAID FEED DOG WEB BEING PROVIDED WITH A NEEDLE ACCOMMODATING APERTURE FORMED AS A NARROW SLOT EXTENDING FROM SAID LINT CLEARING APERTURE AND DISPOSED BENEATH SAID NEEDLE APERTURE IN SAID THROAT PLATE. 